to the advance of keyboard technique. The arts of organ-playing and of composition for the organ were doubtless developed largely outside the churches, though in the 16th and 17th centuries they came into important use in church worship.
Organ-making was originally in the hands of monks, but by about
1500 it began to be widely undertaken as a general trade, so that we encounter
from that time the names of many organ-builders. No sure estimate
can be made of the number of instruments in use at any given period,
but it is clear that by the 17th century they were common and that the
ambition for mechanical improvement was thoroughly awakened.
The mechanical problems of organ-making are manifold. They are usually grouped under three heads—the pipe-work, the wind-supply, and the action. Under the first belong questions regarding the selection and preparation of metal and wood for the pipes, the exact shape and proportions of the pipes with reference to pitch and quality of tone (including the invention of those varying types of structure that belong to distinct 'stops' or 'registers'), and many niceties in the adjustment of the 'mouth' or the reed by which the tone is actually produced. Under the head of wind-supply fall the problems of pumping air into a reservoir or 'bellows,' where somehow it can be brought under a steady pressure and then distributed by tubes to the 'wind-chests' under the pipes so as to be ready for delivery into the pipes as wanted. It is remarkable how much difficulty has been encountered in avoiding leakage and maintaining a uniform pressure. Under the 'action' comes the adjustment of one or more keyboards to the valves admitting the air to the pipes, with the control of the several sets of pipes by stop-handles, every connection having to be made easy, prompt and noiseless. Not until about the 17th century did the modern notion fully emerge of uniting several distinct organs, each with its own keyboard, into one instrument, though more than one keyboard had often been used before. The addition of a pedal keyboard was common from the 15th century. Among special devices, that of the 'swell' in some form (to vary the loudness of some of the tones) is of great utility, but it is doubtful if it appeared before the early 18th century.
The making of large organs differed from other branches of instrument-making in that most or all of the work was originally done not in fixed factories, as now, but on the spot, so that organ-makers moved from place to place as their services were required. Each maker had his own patterns or models, and details varied indefinitely.
103. The Rise of the Organ Style.—The problem of forms of composition for the organ remained unsolved far into the 17th century. The earlier experiments were strictly contrapuntal and modeled closely upon vocal styles. Yet it was seen that the instrument was capable of much more—massive chord-suc-
